Re-transmitter and digital broadcast receiving system

ABSTRACT

Information indicating which of channels is selected in a digital broadcasting receiver  17  is fed from a control signal transmitter  16  to a retransmitter  14.  A terrestrial wave digital broadcasting wave from a transmitting station is inputted to a channel selection filter  6  through an indoor receiving antenna  1  and an automatic gain controller  4  in the retransmitter  14,  and only a signal having a frequency component corresponding to the channel selected by the digital broadcasting receiver  17  is extracted, and is transmitted toward the digital broadcasting receiver  17  by a retransmission indoor antenna  13  through a variable gain amplifier  7.

TECHNICAL FIELD

The present invention relates to a retransmitter that receives digitalbroadcasting and retransmits the received digital broadcasting to adigital broadcasting receiver, and a digital broadcasting receivingsystem.

BACKGROUND ART

In a digital broadcasting system, a video/audio signal is compressedusing a digital signal compression technique, and a stream (a transportstream) obtained by subjecting video/audio digital signals in aplurality of programs to time-division multiplexing is broadcast. On theother hand, a broadcasting receiver that receives such digitalbroadcasting selects one of a plurality of channels in digitalbroadcasting received through an antenna by a tuner, selects one of aplurality of programs included in the one channel by demultiplexingprocessing, and decodes a digital signal on the selected channel tooutput a video/audio signal.

When terrestrial wave digital broadcasting is received, a usage way inwhich an indoor antenna is used is assumed. However, it is expected thata receiving error occurs because a sufficient quality of a receivingsignal is not obtained depending on the positional relationship amongthe indoor antenna, a window of a house, and a transmitting station.Therefore, it is considered that a retransmitter (repeater) is placed atthe window of the house, for example, to amplify a digital broadcastingwave received by an antenna of the retransmitter and emit the amplifieddigital broadcasting wave toward the indoor antenna of the digitalbroadcasting receiver.

When such retransmission is made, however, oscillation easily occurs bycoupling an input and an output. Therefore, the distance between areceiving antenna and a transmission antenna must be increased, therebyincreasing the size of the retransmitter. Further, it is considered thatretransmission is made at a frequency different from a broadcastingfrequency. However, a digital broadcasting signal is fed with serviceinformation added thereto. When the frequency is changed byretransmission, the actual receiving frequency and the frequency of theservice information do not coincide with each other on the side of thereceiver. Consequently, the service information must be rewritten andretransmitted by the retransmitter, so that the configuration becomescomplicated, resulting in increased cost.

In view of the foregoing circumstances, an object of the presentinvention is to provide a retransmitter and a digital broadcastingreceiving system that can suitably make retransmission without changinga frequency.

DISCLOSURE OF INVENTION

In order to solve the above-mentioned problem, a retransmitter accordingto the present invention is characterized by comprising a high-frequencyinput unit to which a receiving antenna for receiving a digitalbroadcasting wave is connected, a high-frequency output unit to which aretransmission antenna for retransmitting the digital broadcasting waveis connected, means for acquiring a frequency selection signal which isa signal fed from a digital broadcasting receiver and corresponds toindication as to which channel is selected by the digital broadcastingreceiver, and selecting and feeding means for selecting, out ofhigh-frequency signals inputted from the high-frequency input unit, thehigh-frequency signal having a frequency corresponding to the frequencyselection signal and feeding the selected high frequency signal to thehigh-frequency output unit.

In the above-mentioned configuration, when the channel is selected inthe digital broadcasting receiver, the selected channel is recognized onthe side of the retransmitter, and the high-frequency signal (digitalbroadcasting wave) having the frequency corresponding to the selectedchannel out of the high-frequency signals inputted from thehigh-frequency input unit is selected and fed to the high-frequencyoutput unit, and is fed to the digital broadcasting receiver by theretransmission antenna.

The retransmitted may be so configured that an indoor receiving antennais mounted as the receiving antenna on the high-frequency input unit,the retransmission antenna is mounted on the high-frequency output unit,and the respective directions of polarization of the indoor receivingantenna and the retransmission antenna are perpendicular to each other.The retransmitter may be so configured that an indoor receiving antennais mounted as the receiving antenna on the high-frequency input unit,the retransmission antenna is mounted on the high-frequency output unit,and the indoor receiving antenna and the retransmission antenna arearranged with a conductor interposed therebetween such that therespective directions of transmission are opposite to each other.

The selecting and feeding means may comprise first gain control meansfor making the level of the high-frequency signal inputted from thehigh-frequency input unit constant, a pass frequency variable filter forselecting the high-frequency signal having the frequency correspondingto the frequency selection signal, and second gain control means forcontrolling transmission power of the selected high-frequency signal.

The retransmitter may be so configured as to further comprise means foracquiring an ON/OFF control signal fed from the digital broadcastingreceiver and a power switch, and as to be turned on and off undercontrol from the digital broadcasting receiver. The retransmitter may beso configured as to further comprise means for acquiring a gain controlsignal fed from the digital broadcasting receiver and feeding a controlsignal to the second gain control means, and that the transmission powerof the high-frequency signal is controlled by the second gain controlmeans under control from the digital broadcasting receiver.

The retransmitter may be so configured that a signal from the digitalbroadcasting receiver is received by wireless.

Furthermore, a digital broadcasting receiving system according to thepresent invention is characterized by comprising any one of theabove-mentioned retransmitters, and a digital broadcasting receiverhaving means for feeding a signal to the retransmitter.

In the digital broadcasting receiving system, the digital broadcastingreceiver may comprise selecting and controlling means for performingprocessing for acquiring the quality of a receiving signal of a digitalbroadcasting wave from the retransmitter, processing for acquiring thequality of a receiving signal of a digital broadcasting wave from atransmitting station, and processing for comparing the qualities of boththe receiving signals to judge which of the digital broadcasting wavesis to be employed.

A digital broadcasting receiving system according to the presentinvention is a digital broadcasting receiving system comprising aretransmitter in which the respective directions of polarization of anindoor receiving antenna and a retransmission antenna are perpendicularto each other, and a digital broadcasting receiver having means forfeeding a signal to the retransmitter, wherein the digital broadcastingreceiver may comprise a receiving antenna having a first receivingelement for receiving a digital broadcasting wave which is ahorizontally polarized wave and a second receiving element for receivinga digital broadcasting wave which is a vertically polarized wave, andselecting and controlling means for performing processing for selectingone of the elements and acquiring the quality of the receiving signal ofthe digital broadcasting wave from the retransmitter, processing forselecting the other element and acquiring the quality of the receivingsignal of the digital broadcasting wave from the transmitting station,and processing for comparing the qualities of both the receiving signalsto judge which of the digital broadcasting waves is to be employed.

The digital broadcasting receiving system may be so configured as tostore in a memory the results of judgment for each of channels by theselecting and controlling means, and utilizing, when the channel forwhich the results of the judgment have already been stored is selected,the results of the judgment which have already been stored, to omit theprocessing for the judgment by the selecting and controlling means.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing, in a digital broadcasting receivingsystem according to an embodiment of the present invention, a digitalbroadcasting receiver in detail;

FIG. 2 is a block diagram showing, in a digital broadcasting receivingsystem according to an embodiment of the present invention, aretransmitter in detail; and

FIG. 3 is a perspective view showing an antenna attached to aretransmitter used in a digital broadcasting receiving system accordingto an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described on the basis ofFIGS. 1 to 3.

In FIG. 1, an indoor antenna 15 has a first receiving element 15 a forreceiving a digital broadcasting wave which is a horizontally polarizedwave and a second receiving element 15 b for receiving a digitalbroadcasting wave which is a vertically polarized wave. Processing forjudging which of the elements feeds a receiving signal to be employed isperformed by a terrestrial wave digital tuner 21 on the basis of acommand from a microcomputer 31.

The terrestrial wave digital tuner 21 extracts, out of receivedhigh-frequency digital modulation signals (digital broadcasting waves),the digital modulation signal having a particular frequency. Theterrestrial wave digital tuner 21 comprises a demodulation circuit, aninverse interleave circuit, an error correcting circuit, and so on,thereby demodulating the selected digital modulation signal to output atransport stream. Further, the terrestrial wave digital tuner 21produces the C/N (carrier-to-noise ratio) or the error rate (the valueof the quality of a receiving signal) of the received digitalbroadcasting wave, and feeds the produced C/N or error rate to themicrocomputer 31.

A demultiplexer (DEMUX) 22 separates the transport stream received fromthe terrestrial wave digital tuner 21 into a video stream and an audiostream based on MPEG2 (Moving Picture Experts Group2) and PSI/SI(Program Specific Information/Service Information). The demultiplexer 22feeds the video stream and the audio stream to an AV decoder 23, andfeeds the PSI/SI to the microcomputer 31. A plurality of channels aremultiplexed on the transport stream. Processing for selecting any of thechannels can be performed by extracting from the PSI/SI data indicatingwhich of packet IDs is used to multiplex the arbitrary channel in thetransport stream. Further, the transport stream can be selected on thebasis of information in the PSI/SI.

The AV decoder 23 comprises a video decoder for decoding the videostream and an audio decoder for decoding the audio stream. The videodecoder decodes a variable length code which has been inputted, to finda quantization factor and a motion vector, thereby carrying out inverseDCT (Discrete Cosine Transformation), motion compensation control basedon the motion vector, and the like. The audio decoder decodes a codedsignal which has been inputted, to produce audio data. The video datagenerated by the decoding is outputted to a video processing circuit 24,and the audio data is outputted to an audio processing circuit 25.

The video processing circuit 24 receives the video data from the AVdecoder 23, and subjects the received video data to digital-to-analog(D/A) conversion, to produce a video signal. The audio signal processingcircuit 25 receives the audio data outputted from the AV decoder 4, andsubjects the received audio data to D/A conversion, to produce an analogsignal of a right (R) sound and an analog signal of a left (L) sound. Adrive circuit 26 receives the video signal, and produces an RGB signaland a synchronizing signal, to drive a CRT 27. A speaker 33 receives theanalog audio signal, to output an audio.

An OSD (On-Screen Display) circuit 30 outputs to an adder 34 bit mapdata based on character information and figure information which areinstructed to output from the microcomputer 31. The adder 34superimposes the bit map data into a video.

A remote control transmitter 28 is a transmitter for sending out acommand to a broadcasting receiver 17. The remote control transmitter 28is provided with a power key, a channel designation key, and so on. Whenthe keys provided in the remote control transmitter 28 are operated,signal light (a remote control signal) meaning a command correspondingto the keys is sent out from a light emitter (not shown). A remotecontrol signal receiver 29 receives the signal light, converts thereceived signal light into an electric signal, and feeds the electricsignal to the microcomputer 31.

A memory (e.g., an EEPROM (Electrically Erasable and ProgrammableMemory) 32 stores various types of programs for performing predeterminedoperations, and others. Further, the memory 32 stores informationrelated to the direction of polarization of a direct digitalbroadcasting wave from a broadcasting station (i.e., information whichof the first receiving element 15 a and the second receiving element 15b receives a direct digital broadcasting wave from the broadcastingstation). A user can enter the information using the remote controltransmitter 28, a setting switch (not shown), etc. Further, the memory32 stores the C/N or the error rate (the value of the quality of areceiving signal) acquired by the tuner 21 for each of channels.

A control signal transmitter 16 feeds various types of control signals(e.g., an infrared signal) to a retransmitter 14 on the basis of acommand from the microcomputer 31. The microcomputer 31 performsprocessing for driving the control signal transmitter 16 in order tocontrol the retransmitter 14 and selection control as to whether thedirect digital broadcasting wave from the broadcasting station isemployed or a digital broadcasting wave from the retransmitter 14 isemployed in addition to program selection processing by the user usingthe remote control transmitter 28 or the like. The selection controlwill be described in detail later.

As shown in FIG. 2, the retransmitter 14 is provided with an RF(high-frequency) input unit 3 having a switch 3 a. The switch 3 a hastwo inputs. An indoor receiving antenna 1 is connected to one of theinputs, and an outdoor receiving antenna (not shown) can be connected tothe other input through an antenna connector 2. The switch 3 a ismanually operated by the user. A terrestrial wave digital broadcastingwave from a transmitting station (not shown) is converted into anelectric signal by the indoor receiving antenna 1 or the outdoorreceiving antenna, and the electric signal is inputted to an automaticgain controller (AGC) 4 through the RF input unit 3.

The automatic gain controller 4 is so configured as to input an outputsignal fed back from a detector (DET) 5, to keep the level of areceiving signal constant. Specifically, the automatic gain controller 4cancels the level fluctuation of a transmission path between thetransmitting station and the indoor receiving antenna 1 and operatessuch that the level of a receiving signal inputted to a channelselection filter 6 becomes constant.

The channel selection filter 6 can vary a frequency at its pass centerby an applied control voltage. The control voltage is applied from acontrol signal demodulator (Dec) 10, and corresponds to a channelselected in the digital broadcasting receiver 17. A signal having afrequency component corresponding to the channel selected in the digitalbroadcasting receiver 17 is extracted by the channel selection filter 6,and is fed to a variable gain amplifier (Gain) 7.

The variable gain amplifier 7 inputs a control voltage fed by thecontrol signal demodulator 10, amplifies the signal at a gain based onthe control voltage, and feeds the amplified signal to a low-pass filter(LPF) 8. The low-pass filter (LPF) 8 reduces higher harmonics includedin the signal, and feeds the signal to a retransmission indoor antenna13. A digital broadcasting wave having a frequency componentcorresponding to the channel selected in the digital broadcastingreceiver 17 is transmitted toward the digital broadcasting receiver 17by the retransmission indoor antenna 13.

The retransmission indoor antenna 13 and the indoor receiving antenna 1are arranged with a flat plate-shaped conductor 18 in an approximatelysquare shape interposed therebetween such that the respective directionsof transmission are opposite to each other, to configure one antennaset, as shown in FIG. 3. The respective directions of polarization ofthe indoor receiving antenna 1 and the retransmission indoor antenna 1are perpendicular to each other. The retransmission device 14 is in aform in which it is accommodated in a case sealed so as not to besubjected to radio interference by transmission/receiving and is addedto the antenna set.

A signal receiver 9 receives a control signal from the control signaltransmitter 16 provided on the side of the digital broadcasting receiver17, converts the received control signal into an electric signal, andfeeds the electric signal to the control signal demodulator 10. Thecontrol signal demodulator 10 demodulates the received control signal todecode an instruction, to carry out ON/OFF control of a power switch 11,gain control of the variable gain amplifier 7, and change control for afrequency at the pass center of the channel selection filter 6. In orderto carry out the change control for the frequency at the pass center,the retransmitter 14 may comprise a correspondence table between acontrol signal (a code) from the digital broadcasting receiver 17 and acontrol voltage value (a control voltage applied to the channelselection filter 6). Alternatively, a signal representing a controlvoltage value (a control voltage applied to the channel selection filter6) itself based on the selected channel may be fed from the digitalbroadcasting receiver 17. The power switch 11 is a switch for choosingwhether or not power from a power input unit 12 is supplied to theautomatic gain controller 4 or the like (ON/OFF of the retransmitter14). The power from the power input unit 12 is always supplied to thecontrol signal demodulator 10 without through the power switch 11.

The control signal transmitter 16 provided on the side of the digitalbroadcasting receiver 17 is controlled by the microcomputer 31 containedin the digital broadcasting receiver 17. The microcomputer 31 drives thecontrol signal transmitter 16 on the basis of a channel selection signalwhich will be received when the user selects the channel in the remotecontrol transmitter 28, and transmits to the retransmitter 14information indicating which channel is selected (which frequency shouldbe selected and passed). Similarly, the control signal transmitter 16 isdriven, thereby making it possible to feed to the retransmitter 14signals for carrying out ON/OFF control of the power switch 11 and gaincontrol of the variable gain amplifier 7.

Description is now made of receiving processing by a digitalbroadcasting receiving system. As the setting of such a system, theinstallation of the retransmitter 14 is first adjusted. In theadjustment of the installation, a plane of polarization of the indoorreceiving antenna 1 coincides with the direction of polarization of thedirect digital broadcasting wave from the broadcasting station(consequently, the direction of polarization of a retransmitted wave isperpendicular to the direction of polarization of the direct digitalbroadcasting wave). Further, the direction of polarization of the directdigital broadcasting wave from the broadcasting station is registered inthe digital broadcasting receiver 17 so that the plane of polarizationof radio waves to be received by the indoor antenna 15 can be recognizedwhen the direction of polarization of the indoor antenna 15 is switchedin order to select and receive the direct wave and the retransmittedwave. When the direct digital broadcasting wave from the transmittingstation is a horizontally polarized wave, for example, the retransmittedwave is a vertically polarized wave. Therefore, the digital broadcastingreceiver 17 performs processing for employing the receiving signal fromthe second element 15 b in the indoor antenna 15 when it receives theretransmitted wave, while performing processing for employing thereceiving signal from the first element 15 a when it receives the directwave which is a horizontally polarized wave.

When the digital broadcasting receiver 17 is turned on, an instructionto turn on the power to the retransmitter 14 is not issued at thebeginning, and the receiving of the direct digital broadcasting wavefrom the transmitting station is tried by the indoor receiving antenna15. At this time, the direct wave which is a horizontally polarized waveis received. Therefore, the receiving signal from the first element 15 ais employed, and the value of the quality of the receiving signal atthis time is stored in the memory 32. The digital broadcasting receiver17 then transmits a signal to be a command to turn on the power, asignal indicating which channel is selected, and so on to theretransmitter 14. Further, switching processing is performed such thatthe receiving signal from the second element 15 b is employed.

The retransmitter 14 receives the above-mentioned signal in the controlsignal receiver 9. The control signal demodulator 10 demodulates theabove-mentioned signal to grasp the contents of control, to turn on thepower switch 11 as well as generate a control voltage corresponding tothe center frequency of the channel selection filter 6 in correspondencewith the selected channel. Further, a control voltage for the variablegain amplifier 7 for determining the level of a transmission output isalso generated. By such processing, out of broadcasting waves receivedin the indoor receiving antenna 1, the broadcasting wave on the channelwhich will be received by the digital broadcasting receiver 17 istransmitted from the retransmission indoor antenna 13 as a broadcastingwave which is a polarized wave perpendicular to the indoor receivingantenna 1.

The digital broadcasting receiver 17 receives the broadcasting wave fromthe retransmitter 14 in the second element 15 b, to acquire the value ofthe receiving quality thereof. A control signal is transmitted to theretransmitter 14 so as to control transmission power from the variablegain amplifier 7 such that the value of the receiving quality of thebroadcasting wave from the retransmitter 14 is the best while comparingthe value of the receiving quality of the broadcasting wave from theretransmitter 14 and the value of the receiving quality of the directwave already stored in the memory 32. When there is no case where thevalue of the receiving quality of the broadcasting wave from theretransmitter 14 exceeds the value of the receiving quality of thedirect wave already stored in the memory 32, the digital broadcastingreceiver 17 feeds a command signal for turning off the power to theretransmitter 14 such that the power switch 11 is turned off in order toperform direct receiving from the transmitting station without using theretransmitter 14. The digital broadcasting receiver 17 employs the firstelement 15 a in the indoor receiving antenna 15 to change the directionof polarization of the indoor receiving antenna 15 for the purpose ofreceiving the direct broadcasting wave. On the other hand, when thevalue of the receiving quality of the broadcasting wave from theretransmitter 14 exceeds the value of the receiving quality of thedirect wave stored in the memory 32, the retransmitter 14 remains in astate where the power thereto is turned on, and the indoor antenna 15remains in a state where the second element 15 b is employed.

When a viewer operates the remote control transmitter 28 to change thechannel, processing for selecting one of the elements in the indoorreceiving antenna 15 and acquiring the quality of the receiving signalof the digital broadcasting wave from the retransmitter 14, processingfor selecting the other element and acquiring the quality of thereceiving signal of the digital broadcasting wave from the transmittingstation, and processing for comparing the qualities of both thereceiving signals and judging which of the digital broadcasting waves isto be employed are performed, as in the foregoing.

When the viewer turns off the power to the digital broadcasting receiver17 or switches the broadcasting receiving mode into a mode for receivinga broadcasting wave other than a terrestrial wave, for example, asatellite system or a cable, the digital broadcasting receiver 17 feedsa control signal by the control signal transmitter 16 to turn off thepower switch 11 in the retransmitter 14.

If it is judged once which of the direct wave and the retransmitted waveis preferable with respect to each of the channels, the judgment may beregistered in the memory 32 in the digital broadcasting receiver 17, notto perform an operation for selecting and confirming preferablereceiving conditions of the direct wave/retransmitted wave at the timeof changing the channel. It is considered that such a period duringwhich the selecting and confirming operation is not performed is aperiod to the next day or to the time when one week has elapsed, to thetime when a reconfirmation command is next issued to the digitalbroadcasting receiver 17 by the user, or the like. The operation forselecting and confirming the preferable receiving conditions of thedirect wave/retransmitted wave may be performed along with the existentstation channel search made when the system is installed or after theuser moves into a new house. When an area where the system is installedis found, and the receiving conditions of radio waves in the area arefound, it may be previously found which of the direct wave and theretransmitted wave is preferable with respect to each of the channels.In such a case, information may be registered in the memory 32 in thedigital broadcasting receiver 17 without performing a selecting andconfirming operation.

When a stable receiving signal is introduced into a house by a cablefrom an antenna installed outdoors, the outdoor antenna may be connectedto an external antenna input terminal 2, to switch the switch 3 towardthe external antenna input terminal 2.

As described in the foregoing, the retransmitter 14 does not retransmitall broadcasting waves in a broadcasting band but synchronizes with achannel to be received by the digital broadcasting receiver 17 toselectively retransmit only a frequency band on the received channel,thereby making it possible to reduce coupling between transmission andreceiving units. In the present embodiment, the retransmission indoorantenna 13 and the indoor receiving antenna 1 are arranged with theconductor 18 interposed therebetween such that the respective directionsof transmission are opposite to each other, and the respectivedirections of transmission and receiving can be made to actually differfrom each other by 180 degrees, although transmission and receivingpoints come close to each other, thereby making it possible to reducethe detouring of a transmitted wave and a received wave. Further, in thepresent embodiment, the respective directions of polarization of theindoor receiving antenna 1 and the retransmission indoor antenna 13 areperpendicular to each other. Accordingly, the transmitted wave and thereceived wave are easy to separate, thereby making it possible tosuppress oscillation.

As described in the foregoing, according to the present invention, evenwhen the digital broadcasting receiver is installed in a place spacedapart from a window, stable receiving can be performed using the indoorreceiving antenna by a retransmitted wave from the retransmitter. Theretransmitter makes retransmission without changing a frequency from thetransmitting station. Therefore, the necessity of replacing serviceinformation is eliminated, thereby making it possible to simplifycircuits constituting the retransmitter.

1. A retransmitter characterized by comprising: a high-frequency inputunit to which a receiving antenna for receiving a digital broadcastingwave is connected; a high-frequency output unit to which aretransmission antenna for retransmitting the digital broadcasting waveis connected; means for acquiring a frequency selection signal which isa signal fed from a digital broadcasting receiver and corresponds toindication as to which channel is selected by the digital broadcastingreceiver; and selecting and feeding means for selecting, out ofhigh-frequency signals inputted from said high-frequency input unit, thehigh-frequency signal having a frequency corresponding to said frequencyselection signal and feeding the selected high-frequency signal to saidhigh-frequency output unit.
 2. In the retransmitter according to claim1, a retransmitter characterized in that an indoor receiving antenna ismounted as the receiving antenna on said high-frequency input unit, theretransmission antenna is mounted on said high-frequency output unit,and the respective directions of polarization of the indoor receivingantenna and the retransmission antenna are perpendicular to each other.3. In the retransmitter according to claim 1 or 2, a retransmittercharacterized in that an indoor receiving antenna is mounted as thereceiving antenna on said high-frequency input unit, the retransmissionantenna is mounted on said high-frequency output unit, and the indoorreceiving antenna and the retransmission antenna are arranged with aconductor interposed therebetween such that the respective directions oftransmission are opposite to each other.
 4. In the retransmitteraccording to claim 1 or 2, a retransmitter characterized in that saidselecting and feeding means comprises first gain control means formaking the level of the high-frequency signal inputted from thehigh-frequency input unit constant, a pass frequency variable filter forselecting the high-frequency signal having the frequency correspondingto the frequency selection signal, and second gain control means forcontrolling transmission power of the selected high-frequency signal. 5.In the retransmitter according to claim 1 or 2, a retransmittercharacterized by further comprising means for acquiring an ON/OFFcontrol signal fed from said digital broadcasting receiver and a powerswitch, and by being turned on and off under control from said digitalbroadcasting receiver.
 6. In the retransmitter according to claim 1 or2, a retransmitter characterized by further comprising means foracquiring a gain control signal fed from said digital broadcastingreceiver and feeding a control signal to the second gain control means,and that the transmission power of the high-frequency signal iscontrolled by the second gain control means under control from saiddigital broadcasting receiver.
 7. In the retransmitter according toclaim 1 or 2, a retransmitter characterized in that a signal from saiddigital broadcasting receiver is received by wireless.
 8. A digitalbroadcasting receiving system characterized by comprising: theretransmitter according to claim 1 or 2; and a digital broadcastingreceiver having means for feeding a signal to the retransmitter.
 9. Inthe digital broadcasting receiving system according to claim 8, adigital broadcasting receiving system characterized in that the digitalbroadcasting receiver comprises selecting and controlling means forperforming processing for acquiring the quality of a receiving signal ofa digital broadcasting wave from the retransmitter, processing foracquiring the quality of a receiving signal of a digital broadcastingwave from a transmitting station, and processing for comparing thequalities of both the receiving signals to judge which of the digitalbroadcasting waves is to be employed.
 10. A digital broadcastingreceiving system comprising the retransmitter according to claim 2; anda digital broadcasting receiver having means for feeding a signal to theretransmitter, characterized in that the digital broadcasting receivercomprises an indoor receiving antenna having a first receiving elementfor receiving a digital broadcasting wave which is a horizontallypolarized wave and a second receiving element for receiving a digitalbroadcasting wave which is a vertically polarized wave, and selectingand controlling means for performing processing for selecting one of theelements and acquiring the quality of the receiving signal of thedigital broadcasting wave from the retransmitter, processing forselecting the other element and acquiring the quality of the receivingsignal of the digital broadcasting wave from the transmitting station,and processing for comparing the qualities of both the receiving signalsto judge which of the digital broadcasting waves is to be employed. 11.In the digital broadcasting receiving system according to claim 9, adigital broadcasting receiving system characterized by storing in amemory the results of the judgment for each of the channels by saidselecting and controlling means, and utilizing, when the channel forwhich the results of the judgment have already been stored is selected,the results of the judgment which have already been stored, to omit theprocessing for the judgment by the selecting and controlling means.